Silicon and silicon-containing films are used for a wide variety of applications in the semiconductor industry. Silicon films include polycrystalline silicon (poly-Si) and epitaxial silicon, and silicon-containing film include silicon germanium (SiGe), silicon germanium carbide (SiGeC), silicon carbide (SiC), and silicon nitride (SiN). As circuit geometries shrink to ever smaller feature sizes, lower deposition temperatures are preferred, for example because of introduction of new materials into semiconductor devices and reduction of thermal budgets of shallow implants in source and drain regions. Moreover, it is evident that non-selective (blanket) and selective deposition of silicon-containing films will be needed for future devices. For example, semiconductor fabrication requires tight specification limits on thickness and resistivity for epitaxial silicon films. Epitaxial silicon deposition can be a first step in a process flow where the crystal lattice of the bulk silicon is extended through growth of a new silicon-containing layer that may have a different doping level than the bulk. Matching target epitaxial film thickness and resistivity parameters is important for the subsequent fabrication of properly functioning devices.
One example of the use of selective deposition of epitaxial silicon-containing films is for manufacturing silicon-on-insulator (SOI) devices with raised source and drains. During SOI device fabrication, processing may consume an entire silicon film in source and drain regions, thereby requiring extra silicon in these regions that can be provided by selective epitaxial growth (SEG) of silicon-containing films. Selective epitaxial deposition of silicon-containing films can reduce the number of photolithography and etching steps that are needed, which can reduce the overall cost and complexity involved in manufacturing a device. Despite the preference for lower temperature deposition processes, thermal deposition of epitaxial silicon using the traditional silane (SiH4) and dichlorosilane (DCS, SiCl2H2) source gases generally require high deposition temperatures (e.g., greater than about 850-900° C.) to achieve deposition rates that are high enough for the process to be incorporated into processes for manufacturing of devices.
Future device generations will require new methods with low thermal budgets for depositing silicon and silicon-containing films with improved materials and electrical properties, for example thinner films without pinhole defects.